Expandable introducer sheath

ABSTRACT

The present invention comprises a method and device for providing an expandable introducer sheath. The method of employing the inventive device comprises inserting an elongate flexible tubular sheath into a vessel (with a proximal end of the sheath extending proximally outward through the skin), to slidably receive intravascular devices. When a larger size introducer sheath is desired, the sheath is manipulated while still in the vessel to expand its inner diameter to a larger size. In one embodiment, the sheath is made of a shape-memory polymer and is manipulated by inserting a heated mandrel (with an outer diameter larger than the inner diameter of the sheath) within the sheath to cause the sheath to expand to an inner diameter at least approximately equal to an outer diameter of the mandrel. The shape-memory polymer material ensures that the sheath will retain its expanded inner diameter. Alternatively, the sheath is formed from a telescoping multi-tubular arrangement of progressively larger tubes. In any case, insertion of the inventive sheath into the skin requires only a single small puncture which is then only expanded as needed while the sheath remains in place.

This is a Continuation of application Ser. No. 08/269,631, filed Jul. 1,1994, now abandoned, which is a continuation of application Ser. No.07/961,372 filed Oct. 15, 1992, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to the field of sheaths for introducingintravascular catheters. In particular, the present invention relates toa flexible sheath for percutaneously introducing intravascular catheterssuch as an angioplasty catheter.

Angioplasty has gained wide acceptance in recent years as an efficientand effective method for treating various types of vascular diseases. Inparticular, angioplasty is widely used for opening stenoses in thecoronary arteries, although it is also used for treatment of stenoses inother parts of the vascular system.

The most widely used form of angioplasty makes use of an introducersheath positioned at the entry point of the intravascular catheters intothe cardiovascular system. For instance, the distal end of theintroducer sheath is inserted into the femoral artery located in thegroin of the patient and pushed distally through the artery until thesheath is firmly seated within the artery. The proximal end of theintroducer sheath protrudes outside of the patient's body to provide anentryway for subsequent insertion of additional or other intravasculardevices. The additional or other intravascular devices include guidecatheters, guide wires, and balloon dilatation catheters, orangiographic catheters as well as other therapeutic and diagnosticintravascular catheters.

The introducer sheath typically is inserted into the vessel through theskin percutaneously. Prior to the development of percutaneous insertionmethod, entry into the vessel was achieved by cutting the skin with ascalpel to expose the vessel of interest and then inserting a needle orother puncture apparatus through the vessel wall to facilitate entry ofthe introducer sheath and/or an intravascular catheter. In thepercutaneous insertion technique, a needle or similar puncture device isinserted into the skin without first cutting the skin to expose thevessel. The needle is then advanced through the skin (and tissue) untilthe needle enters the vessel of interest.

In the common percutaneous insertion procedure, a distal end of a hollowthin-walled puncture needle (alternatively, a Seldinger needle may beused) is inserted through the skin (and underlying tissue) and through awall of the desired vessel. A proximal end of the needle remains outsideof the surface of the skin. Next, a distal end of a thin flexible wireis inserted into the proximal end of the needle and advancedtherethrough until a distal end of the wire extends distally beyond thedistal end of the needle and into the vessel. A proximal end of the wireremains outside, extending through the proximal end of the needle. Whilemaintaining the flexible wire in position within the vessel, the needleis proximally withdrawn over the wire until completely removed from thevessel and the skin (and underlying tissue).

Next, the physician prepares an introducer sheath outside the patient'sbody by inserting a distal end of a dilator (e.g., an elongate flexiblecylinder with a bore extending therethrough) into a proximal end of theflexible plastic introducer sheath and advances the dilatortherethrough. The dilator is advanced until a distal tip portion of thedilator extends distally beyond a distal end of the sheath and aproximal portion of the dilator remains outside of the proximal end ofthe sheath. The distal tip portion of the dilator has a tapered outerdiameter that gradually increases proximally to an enlarged diameteradjacent the distal end of the sheath. By means of a snap fit orfriction fit, the proximal portion of the dilator is releasably securedto the proximal portion of the sheath so that the dilator and sheathcomprise an assembled unit for insertion into the vessel.

The distal end of the dilator (with the sheath loaded thereon) isthreaded over the proximal end of the wire and inserted through the skin(and underlying tissue) and into the vessel by distally advancing thedilator and sheath over the wire. Because the dilator is longer than thesheath, the distal end of the dilator enters the vessel before thedistal end of the sheath and the dilator and sheath are advancedtogether until the distal portion of the sheath extends within thevessel. The tapered distal tip portion of the dilator gradually expandsthe opening in the vessel wall as the dilator moves there through. Withthe distal end of the sheath properly positioned (extending into thevessel), the proximal end of the sheath and the proximal end of thedilator remain outside the surface of the skin. Next, while maintainingthe sheath in place within the vessel and after disengaging the dilatorfrom the sheath, the dilator and wire are removed by proximallywithdrawing them from inside the sheath. With the sheath in place, thepuncture site is now ready for the widely known transluminal angioplastyprocedure or other procedure involving intravascular catheters. Thesheath provides a convenient and protective entryway for intravasculardevices into the cardiovascular system.

In the case of an angioplasty procedure, the next step includesinserting a distal end of a hollow guide catheter through the sheath andinto the vessel. A proximal end of the guide catheter remains outside ofthe proximal end of the sheath for facilitating insertion ofintravascular devices through the guide catheter. For instance, a guidewire could be inserted through the guide catheter and advanced distallyuntil a distal end of the guide wire is distal to a stenosis in acoronary artery. A balloon dilatation catheter is then threaded over theproximal end of the guide wire and inserted up through the guidecatheter and manipulated to treat a stenosis.

The sheath for introducing the guide catheter and other intravasculardevices facilitates the insertion and withdrawal of intravasculardevices through the skin and underlying tissue into a vessel. The sheathminimizes trauma to the skin puncture site and vessel wall caused by thefrequent insertion and removal of intravascular devices from the vessel.In addition, the introducer sheath prevents backbleeding, i.e., bloodflow exiting the punctured vessel, because the typical sheath has ahemostasis valve carried therein at its proximal end. The hemostasisvalve forms a fluid tight seal about a variety of sizes of intravascularcatheters, guide wires, and the like to prevent a flow of blood out ofthe patient or air into the patient. The hemostasis valve also sealinglycloses when no device extends through the hemostasis valve (and sheath).

Although the inner diameter of the sheath should have a close tolerancewith the outer diameter of the intravascular device, it is desirable tohave some spacing between the sheath and intravascular device forperfusion or for drug infusion flow techniques through that spacing. Aside arm with a 3-way valve connector connected to the proximal end orhub of the sheath can be used for blood perfusion or drug infusion.

Reasons for minimizing the size of a sheath include minimizing the sizeof the opening in the vessel and the skin puncture site, increasing thestability of the sheath within the skin puncture site, and reducing thetime for this puncture site to heal. There are two reasons that thistime is of interest. First, ensuring the proper clotting of this openingrequires the attention of trained personnel for several minutes (e.g.,15 minutes) after the sheath is removed. Second, patients need to remainimmobile for many hours after the sheath is removed to ensure that theclotted opening in the vessel does not reopen. These healing times areso long because patients typically have Heparin®, an anticoagulant, intheir cardiovascular systems. It is desirable to reduce both of thesetimes.

Although it is desirable to minimize the outer diameter of theintroducer sheath, an intravascular device having an outer diameterlarger than the inner diameter of the introducer sheath already in placemay be required later in the surgical procedure. These larger sizeintravascular devices require the use of a larger size introducer sheathand accordingly, necessitate exchanging the first introducer sheath foranother introducer sheath having a larger inner diameter.

For example, this situation frequently arises because a smaller sizeintroducer sheath is required for angiography procedures and a largersize introducer sheath is required for an angioplasty procedure. Forexample, a procedure using angiography catheters typically would beperformed with an introducer sheath having a size 5 or 6 French innerdiameter. However, present day angioplasty guide catheters (throughwhich a angioplasty dilation catheter would pass) are generally toolarge to fit through size 5 and 6 French introducer sheaths.Accordingly, if it were determined that an angioplasty procedure wererequired, then a larger inner diameter size introducer sheath (e.g., 7or 8 French) would be needed to accommodate the outer diameter of anangioplasty guide catheter. If an adjunctive procedure such as anatherectomy or stent placement procedure would be necessary after orinstead of the angioplasty procedure, an even larger size introducersheath would be required.

With the possibility of these different sized introducer sheaths beingrequired, the physician is faced with a dilemma. It is highly desirableto use the smallest size introducer sheath possible to minimize the sizeof the opening in the skin and in the vessel (e.g., femoral artery).However, if one selects an introducer sheath that is too small toaccommodate all the necessary intravascular devices, then the smallersize introducer sheath would have to be later exchanged for a largerone. Confronted by this choice, physicians commonly choose to insert anintroducer sheath of a size large enough to easily accommodate allpotential intravascular devices. This means that an introducer sheathfrequently is selected that is much larger than necessary and thisinitial choice for the larger introducer sheath may sacrifice the highlydesirable goal of minimizing the size of the opening in the artery walland skin puncture site.

In a case where a smaller inner diameter size sheath was initiallyselected and must be removed to be replaced by a larger inner diametersize sheath, all intravascular devices from within the vessel typicallymust be removed (with the possible exception of a coronary guide wire).Next, the smaller size sheath must be removed from the vessel and skinsurface puncture site. To do so, with the sheath still in place withinthe vessel, the physician reinserts the dilator into the sheath untilthe dilator extends within the vessel beyond the sheath (and the sheathlocks with the dilator) so that the wire may be threaded through thedilator until the distal end of the wire extends through the vesseldistally beyond the distal end of the dilator. While leaving the wire inplace within the vessel, the dilator and sheath are removed from withinthe vessel.

Next, to place a larger introducer sheath within the vessel, a physicianwould repeat the entire percutaneous puncture insertion method forintroducer sheaths as previously described (except for not using apuncture needle because the wire already extends the vessel). If thisprocedure is performed at a new puncture site along the vessel, then anew puncture site would be needed. In any case, repeating thepercutaneous insertion procedure traumatizes the endothelium layer ofthe vessel wall, the surrounding tissue, and the skin much more thanperforming the percutaneous insertion technique only once. Moreover,many patients receiving angioplasty treatment already suffer fromdiseased arterial walls which magnifies the problem of repetitioustrauma to vessel wall.

Because of the large number of devices of varying sizes which may beused in a combined angiography/angioplasty, or adjunctive procedure, theconventional introducer sheath has many deficiencies. One majordeficiency is that there is no mechanism for increasing the size of theintroducer sheath (once having been inserted) other than by replacingthe smaller size introducer sheath with a second larger size introducersheath through a second percutaneous insertion procedure. Thisdeficiency drives the physician to reluctantly select an introducersheath with a size potentially much larger than necessary, needlesslyincreasing the size and healing time of the opening created in thevessel wall and skin surface. This results, in substantial part, inincreased patient recuperation time which typically dictates anovernight stay in the hospital for a procedure that otherwise could bedone on an outpatient basis.

Various attempts have been made at solving the problem of having anexpandable or variable size introducer device. For example, Grayzel U.S.Pat. No. 4,921,479 is directed to a removable, expandable sheath forintroducing catheters. The sheath is made of a semi-stiff plastic withmemory and formed in a tubular configuration with a longitudinal slitextending along the entire length of the sheath. The tubular structureis typically coiled about its longitudinal axis so its tubular walloverlaps itself. Upon insertion of a larger diameter intravasculardevice, the tubular sheath enlarges its inner diameter by uncoiling tothe extent necessary to accommodate the catheter inserted therein. TheGrayzel device is disadvantageous because the slit extending the lengthof the sheath permits potential backbleeding and the moveable nature ofthe walls relative to each other can traumatize the vessel possiblycausing a dissection of the vessel wall or at least exacerbating theinjury to the endothelium layer of the vessel wall and the skin tissue.

Another attempt includes Schreck U.S. Pat. No. 4,411,655 which relatesto an expandable cannula for introducing catheters into thecardiovascular system. The cannula is made of a metallic shape-memoryalloy formed into a cylindrical cannula with a plastic sheath coveringthe cannula. The lumenal diameter of the cannula dilates after insertioninto the body vessel as the temperature of the shape-memory alloy isheated by equilibrating to the predetermined body temperature or byapplication of resistance heating or other methods to activate theshape-memory alloy. This device requires an additional plastic sheath tocover the metal alloy cannula, thereby creating an outer diameter largerthan necessary. Moreover, because the cannula is made of a metal alloy,it is inflexible contributing to greater tissue trauma because thecannula will have less "give" when pressing against the surroundingtissue and vessel wall. Moreover, in the embodiment in which the cannulaexpands because of the temperature of the body, there is no choice forthe operator to decide when the cannula expands.

SUMMARY OF THE INVENTION

The present invention comprises a method and device for providing anexpandable introducer sheath. The method of employing the inventivedevice comprises inserting an elongate flexible tubular sheath into avessel (with a proximal end of the sheath extending proximally outwardthrough the skin), to slidably receive intravascular devices. When alarger size introducer sheath is desired, one manipulates the sheathwhile still in the vessel to expand its inner diameter to a larger size.In one embodiment, the sheath is made of a shape-memory polymer and themanipulating step may comprise inserting a heated mandrel (with an outerdiameter larger than the inner diameter of the sheath) within the sheathto cause the sheath to expand to an inner diameter at leastapproximately equal to an outer diameter of the mandrel. Theshape-memory polymer material ensures that the sheath will retain itsexpanded inner diameter.

In another embodiment, the elongate flexible tubular sheath is made of ashape-memory polymer and before placement within the vessel, the sheathis mechanically "formed down" to have an inner diameter smaller than theoriginal size inner diameter formed when the sheath was extruded. Oncein the vessel, the sheath can be manipulated to expand its innerdiameter back to the original size. To do so, a heated mandrel can beinserted into the sheath to cause the sheath to exceed a glasstransition temperature of the polymer material and thereby induce theshape-memory polymer material sheath to "snap back" to its original andlarger size inner diameter.

Another embodiment of the present invention provides an expandable innerdiameter introducer by employing a sheath including a inner sheathtubular portion and an outer sheath coaxially slidable over the innersheath. The outer sheath is shorter than the inner sheath so that whenthe inner sheath is disposed within the vessel and extends proximallyoutward therefrom, the outer sheath is coaxially disposed about theinner sheath proximal to a skin surface. To provide an expanded innerdiameter introducer sheath, the outer sheath is advanced distally overthe inner sheath until within the vessel. Then, while maintaining theouter sheath in the vessel, the inner sheath is withdrawn proximallyfrom within the outer sheath. The outer sheath which remains in thevessel provides an expanded or larger inner diameter introducer sheath.

Of course, in addition to other preferred embodiments described furtherin the detailed description, many other embodiments are contemplatedwhich provide an expandable introducer sheath of the present invention.

The expandable introducer sheath of the present invention facilitatesconvenient percutaneous insertion and removal of intravascular devices.The present invention provides an introducer sheath capable of beingexpanded to have a larger inner diameter when desired without removal ofthe sheath from within the vessel (and while a coronary guide wireremains in the artery). This significantly reduces trauma to the skintissue and punctured vessel (e.g., femoral artery wall) of a patientbecause it alleviates the need to completely remove a smaller introducersheath from within the vessel in exchange for a larger inner diametersheath to be inserted percutaneously in the injurious conventionalmulti-step manner. The sheath is flexible which further reduces traumato the skin and vessel wall because the sheath can "give" and/or "flex"when in contact with these body tissues. The polymeric sheath materialalso reduces the likelihood of thrombogenic activity. The sheath is ofsimple tubular construction having a continuous wall surface along itslength and hub region. This increases the ease of handling the sheathand accentuates blood flow management while reducing a chance ofdissecting or injuring the vessel wall because the continuous smoothsurface of the sheath lacks discontinuities (e.g., longitudinal freeedges and sharp corners like those in the previous devices).

More importantly, an expandable introducer sheath diminishes aphysicians pre-operative dilemma of wanting to use the smallest sizeintroducer sheath to minimize puncture site trauma yet selecting a sizelarge enough to accommodate all the necessary intravascular devices sothat the chosen introducer sheath does not have to be later exchangedfor a larger size sheath. With the present invention, a physician canpercutaneously insert a smaller inner diameter expandable introducersheath into a vessel to minimize puncture site trauma (primarily thesize of the opening in an arterial wall). Then, if at a later time, alarger introducer sheath is required, the physician can manipulate theexpandable introducer sheath to expand its inner diameter instead ofhaving to exchange the smaller size sheath for a larger size sheath.This will lead to reduced patient healing times in at least two ways.First, physicians can initially use the smallest size introducer sheathsuitable and, in many cases (where a larger sheath is not laterrequired), this substantially minimizes the size of the arterial wallopening. Second, even if a larger inner diameter introducer sheath islater required, this alleviates the time-consuming and injuriousconventional technique of removing the smaller sheath and thenre-establishing a larger sheath within the vessel (at the same or adifferent puncture site).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an angioplasty dilatation catheter system includinga guide catheter, dilatation catheter, and guide wire operativelydisposed within an introducer sheath inserted percutaneously through theskin.

FIG. 1B illustrates a puncture needle and guide wire extendingtherethrough extending into a vessel through the skin.

FIG. 1C illustrates an introducer sheath threaded over a dilator withboth extending into the vessel.

FIG. 1D illustrates the introducer sheath extending into the vesselthrough the skin.

FIG. 2A illustrates an expandable introducer sheath of the presentinvention with an intravascular device extending proximally outwardtherefrom.

FIG. 2B illustrates the sheath of the present invention with a mandreladjacent thereto prior to insertion of the mandrel.

FIG. 2C illustrates the mandrel as inserted within the introducer sheathof the present invention.

FIG. 2D illustrates an expanded size of the introducer sheath of thepresent invention after complete insertion and removal of the mandrel.

FIG. 3A illustrates another embodiment of the expandable introducersheath of the present invention in cross-section.

FIG. 3B illustrates the sheath of the present invention prior toinsertion of a mandrel shown adjacent thereto the proximal end thereof.

FIG. 3C illustrates the expandable introducer sheath with a mandrelextending partially therethrough.

FIG. 3D illustrates the sheath of the present invention in its enlargedsize after complete insertion and removal of the mandrel from thesheath.

FIG. 4A illustrates another embodiment of the sheath of the presentinvention including a fold formed in a wall of the sheath and showing amandrel prior to its insertion in the sheath.

FIG. 4B shows a sectional view as taken along lines 4B--4B in FIG. 4A.

FIG. 4C shows the folded sheath embodiment of the present invention witha mandrel inserted partially therethrough.

FIG. 4D illustrates a sectional view as taken along lines 4D--4D in FIG.4C.

FIG. 4E illustrates a sectional view as taken along lines 4E--4E in FIG.4C.

FIG. 4F illustrates a sectional view taken along lines 4F--4F in FIG.4C.

FIG. 4G illustrates the folded sheath embodiment in its expanded sizeafter insertion and removal of the mandrel.

FIG. 5A illustrates another embodiment of the present inventionincluding an outer sheath coaxially disposed on an inner sheath andremaining outside the skin surface.

FIG. 5B shows an enlarged sectional view of a portion of the innersheath and the outer sheath.

FIG. 5C shows the outer sheath disposed within the vessel and the innersheath removed from within the vessel.

FIG. 5D shows an intravascular device 170 extending through the outersheath disposed within the vessel.

FIG. 6A illustrates an expandable introducer sheath of the presentinvention as disposed within a vessel percutaneously.

FIG. 6B illustrates a sheath of the present invention partiallywithdrawn from the vessel and having a rod extending outwardlytherefrom.

FIG. 6C illustrates a removed hub of the sheath in phantom and having alarger diameter outer sheath placed over the first sheath.

FIG. 6D illustrates the second sheath disposed percutaneously within thevessel and extending proximally outward through the skin surface withthe inner long sheath and rod extending proximally outward therefrom.

FIG. 6E illustrates the larger diameter sheath disposed within thevessel after removal of the longer inner sheath and rod.

FIG. 7A illustrates an expandable introducer sheath of the presentinvention including a rib extending longitudnally on an inner wall ofthe sheath.

FIG. 7B illustrates an enlarged sectional view as taken along lines7B--7B in FIG. 7A.

FIG. 7C illustrates a sectional view similar to FIG. 7B except showing aguide catheter disposed within the sheath.

While the above identified drawing features set forth preferredembodiments, other embodiments of the present invention are alsocontemplated, as noted in the discussion. This disclosure presentsillustrative embodiments of the present invention by way ofrepresentation and not limitation. Numerous other modifications andembodiments can be devised by those skilled in the art which fall withinthe scope and spirit of the principles of this invention. The figureshave not been drawn to scale as it has been necessary to enlarge certainportions for clarity. For example, the change in the inner and outerdiameters of the sheath tubing shown before (e.g., FIG. 2B) and afterexpansion (e.g., FIG. 2D) of the sheath has been exaggerated. Inaddition, a hub at a proximal end of the sheath also has been enlargedfor clarity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention comprises a method and apparatus for providing anexpandable introducer sheath. The present invention allows a physicianto initially choose a small size introducer sheath to minimize the sizeof the opening in the arterial wall (e.g., femoral artery) yet have theflexibility of having a larger size introducer sheath without the needto repeat a complete percutaneous insertion procedure (that must beperformed when exchanging a conventional introducer sheath for a secondlarger introducer sheath). To fully understand the advantages of thepresent invention, it is necessary to review the percutaneous insertionprocedure for placing an introducer sheath within a vessel, such as afemoral artery. This will highlight the complexity and disadvantagesthat arise if a percutaneous insertion procedure had to be repeated, andsimultaneously provide insight into the advantages and benefits ofproviding an expandable introducer sheath of the present invention.

I. A Typical Percutaneous Insertion Procedure for Placing an IntroducerSheath within a Vessel

An expandable introducer sheath of the present invention can be employedin many contexts for introducing intravascular and intralumenal deviceswithin the human body. For example, the expandable introducer sheath ofthe present invention may be employed in an angioplasty catheter systemas illustrated generally at 10 in FIG. 1A which is shown employing aconventional-type introducer sheath 12. The conventional(non-expandable) introducer sheath 12 of the catheter system 10 has adistal end 14 and a proximal end 16 with a tubular shaft 18 extendingtherebetween. A tubular entry port 17 extends proximally from theproximal end 16 of the sheath 12. The distal end 14 and a majority ofshaft 18 of the sheath 12 are shown extending within the vessel 11. Aremainder of the shaft 18 and the proximal end 16 of the sheath 12 areshown extending proximally outward from a wall of the vessel 11 throughthe skin tissue 19 and puncture site 20. A side port 21 of the sheath 12extends laterally from the port 17 and provides a connection for fluidcommunication with a flexible tube 13 having a three-arm connector 22for connecting desired devices to control blood flow (e.g. perfusion) ordrug infusion within the vessel. The port 17 also includes a hemostasisvalve 15 carried therein (see FIG. 1D) which provides a fluid-tight sealabout intravascular devices (or other devices) passing through theproximal end of the port 17.

A guide catheter 24 of the catheter system 10 has a flexible shaft 25which extends through the introducer sheath 12 and has a distal end 26extending distally beyond the distal end 14 of the sheath 12 into thevessel 11. A proximal end 27 of the guide catheter 24 extends proximallyoutward outside of the patient's body beyond the port 17 of the sheath12. A threaded luer lock fitting 29 releasably secures the proximal end27 of the guide catheter 24 to a distal end 30 of a Y-adaptor manifold31. A proximal end 32 of the Y-adaptor manifold 31 includes aTouhy-Borst compression seal 33 which forms a fluid-tight seal around ashaft of an angioplasty dilatation balloon catheter 34 (shown extendingthrough the guide catheter 24).

The dilatation catheter 34 of the catheter system 10 has a proximal end35 and a distal end 36 with a balloon 37 formed thereon. The balloon 37is inflatable by an inflation device 38 connected to the proximal end 35of catheter 34 by way of a three-way valve fitting 39. The Y-adaptor 31further includes a side port 40 having a Touhy-Borst compression seal41. The side port 40 is adapted to receive a syringe 42 (via a manifold)containing a radiopaque dye which is injected through the guide catheter24 (via Y-adaptor 31) to the coronary arteries in a conventional manner.A guide wire 43 extends through a distal portion of the dilatationcatheter 34 and, in the case of a single operator angioplasty catheter,the guide wire 43 extends alongside the dilatation catheter through amajority of guide catheter 24 until exiting at the proximal end 32 ofthe Y-adaptor 31.

The introducer sheath 12 provides a pathway through the skin tissue 19(i.e. surface of the skin and the underlying tissue adjacent the vessel)into the vessel 11 to facilitate passage of the guide catheter 24, theballoon catheter 34 and the guide wire 43 in and out of the vessel 11 asdesired. Typically, the introducer sheath 12 is positioned within thevessel 11 through the skin tissue 19 prior to the insertion of anyintravascular device. For example, the sheath 12 may be placed in thevessel 11 through a percutaneous insertion method such as the followingtechnique. A thin walled hollow puncture needle 44, as seen in FIG. 1B,is inserted through the skin tissue 19 so that a distal end of theneedle 44 passes through a wall of the vessel 11 and extends into alumen defined by the vessel 11. Next, a distal end of a thin metal guidewire 46 is inserted into a proximal end of the needle 44 and is threadedtherethrough until a distal end of the wire 46 extends into the vessel11 distally beyond the distal end of the needle 44, while a proximal endof the wire 46 extends proximally outward from a proximal end of theneedle 44 as seen in FIG. 1B. While maintaining the wire 46 in placewithin vessel 11 (by grasping a proximal end of the wire 46), the needle44 is withdrawn proximally over the wire 46 and out of the vessel 11 andthe skin tissue 19 until only the wire 46 remains in the vessel 11.

Next, the sheath 12 must be prepared for insertion into the vessel 11. Adilator 48 (an elongate flexible cylinder having a bore extendingtherethrough) is inserted into the proximal end 16 of the sheath 12. Thedilator 48 is advanced distally therethrough until a distal portion ofthe dilator 48 extends beyond the distal end 14 of the sheath 12 and aproximal portion of the dilator 48 releasably locks (by friction fit andthe like) with and extends outward from the proximal end 16 of thesheath 12. The sheath 12 and dilator 48 now comprise an assembled unitfor insertion into the vessel 11.

To insert the sheath 12 in the vessel, the dilator 48 (with the sheath12 loaded thereon) is advanced distally over the wire 46 until thedistal portion of both the dilator 48 and sheath 12 extend into thevessel 11 and a proximal end of both the dilator 48 and sheath 12 extendproximally outward through the skin tissue 19 as shown in FIG. 1C. Thetapered distal portion of the dilator 48 gradually dilates or expandsthe pathway through the skin tissue 19 and the opening in the wall ofvessel 11 to accomodate the larger outer diameter of the sheath 12. Thedilator 48 also provides rigidity to the thin walled sheath 12 duringinsertion into the vessel.

The sheath 12 (still loaded onto and locked to the dilator 48) isadvanced into the vessel 11 until the port 17 of sheath 12 is proximallyadjacent the skin puncture site 20 (like that shown in FIGS. 1A and 1D).Next, while maintaining the position of the sheath 12 in the vessel 11,the sheath 12 is unlocked from the dilator 48 and the wire 46 anddilator 48 are withdrawn proximally through the proximal end 16 of thesheath 12 until only the sheath 12 remains within the vessel 11 as shownin FIG. 1D. At this point, the sheath 12 is ready to slidably receivethe desired intravascular devices. Typically, the next step involvesthreading the guide catheter 24 through the sheath 12 and advancing andpositioning the guide catheter 24 within the cardiovascular system.After positioning the guide catheter 24, other intravascular componentsare maneuvered through the guide catheter 24 until the configurationshown in FIG. 1A has been achieved. Although FIG. 1A illustrates asingle operator exchange catheter system, other systems such as anover-the-wire or fixed wire dilatation catheter system may be used withan introducer sheath.

Although this is a common technique applied for percutaneously insertingan introducer sheath for introducing intravascular devices, othertechniques may be employed. In any case, after placing the sheath 12 inthe vessel 11 in this manner, the desired diagnostic or therapeuticprocedure may be performed, including an angioplasty procedure using thedesired intravascular treatment. For example, an angiography procedure(which does not use a guide catheter) could be performed for viewing(via fluoroscopy) the coronary arteries to observe the blood flow inthat region.

An angiography typically is performed with a relatively smaller sizecatheter, such as a 5, 6, or 7 French size catheter. A "French" is aunit of measurement which roughly corresponds to one-third of amillimeter (or 0.013 inches), and is used to designate the diameter ofthe catheter or other lumenal intravascular device. Accordingly, a size6 French catheter would have diameter of about 0.078 inches.

Prior to inserting an angiography catheter into a vessel, an introducersheath is typically positioned within a vessel and protrudes out of thepatient's body in the manner previously described. The introducer sheathtypically is selected to have an inner diameter slightly greater thanthe outer diameter of the angiographic catheter. An angiographyprocedure may begin by threading a distal end of an angiography catheterinto the proximal port 17 of sheath 12 and advancing the catheterdistally therethrough into the vessel and through the cardiovascularsystem until its distal end is adjacent the coronary arteries. Theproximal end of the angiographic catheter extends proximally outwardthrough the sheath port 17 outside of the patient's body. After usingthe angiographic catheter to observe the coronary vasculature (or othersystem), the angiography catheter is then removed from thecardiovascular system by withdrawing it proximally out of the sheath 12through port 17.

At this point, one may terminate the surgical procedure. However, anangioplasty procedure may follow the angiography procedure. Anangioplasty procedure using the angioplasty catheter system 10 asdescribed would have a guide catheter as its largest device (indiameter) to pass through the introducer sheath 12. The guide cathetertypically has a size 7, 8, or larger French diameter that is larger thanthe size introducer sheath used for the angiography catheter that wouldstill be in position within the vessel 11. Accordingly, the smaller sizeintroducer sheath used for the angiographic procedure would have to bereplaced with a larger size introducer sheath to accommodate the largersize guide catheter.

To do so, the sheath 12 must be withdrawn proximally out of the vessel11 and skin tissue 19. This includes removing some sutures typicallyused to hold or anchor the proximal end of the sheath in place at thepuncture site 20.

In the case where the original puncture site is to be re-used, theintroducer sheath 12 is removed in the following manner. First, with thesheath 12 still in place within the vessel, the dilator 48 isre-inserted into the sheath 12 and advanced distally therethrough untilboth the sheath 12 and dilator 48 are once again locked together. Next,the wire 46 is threaded through the dilator 48 until extending withinthe vessel 11 distally beyond the dilator 48 and sheath 12. Whilemaintaining the wire 46 within the vessel 11, the dilator 48 and sheath12 are removed from the vessel 11 until both are outside the patient'sbody.

To introduce a new larger introducer sheath, the larger sheath is loadedonto a dilator and both the dilator and sheath are threaded over thewire in place within the vessel 11. The sheath is then positioned withinthe vessel 11 as previously described and the dilator and wire areremoved from within the vessel.

If a second puncture site along the vessel wall is used, then the entirepercutaneous insertion method previously described for insertingintroducer sheath 12 would have to be performed again for the largersize introducer sheath at the new puncture site. This includes thefollowing steps: inserting the puncture needle 44 through skin 19 intothe vessel 11 ; threading the wire 46 through the needle 44 (FIG. 1B);removing the needle 44 from the vessel 11 while maintaining the wire 46within the vessel 11; threading the dilator 48 and sheath 12 over thewire 46 and into the vessel 11 (FIG. 1C); and removing the dilator 48and wire 46 from the sheath 12 resulting in the configuration of FIG.1D.

Performing this second percutaneous insertion procedure wastes time,wastes an additional introducer sheath (and associated wire, needle,dilator), and creates extra bleeding. Moreover, this also createsanother opportunity for bacterial infection, undesired thrombogenicactivity and potential loss of a blood volume. More importantly, in thecase of re-using a puncture site in the vessel wall, inserting a largerintroducer sheath (in exchange for a smaller one) re-traumatizes theopening in the wall of the vessel through which the sheath extends. Thisresults in longer clotting times to close the opening at the end of thesurgical procedure and longer recuperation times to ensure stability inthe healed puncture site in the arterial/vessel wall. In the case ofusing a second puncture site along the vessel, longer clotting andrecuperation times are required because two openings must be closed andstabilized.

Faced with the disadvantages of exchanging introducer sheaths,physicians typically choose an introducer sheath that is larger thannecessary to avoid the possibility of having to perform a sheathexchange. Although less traumatic than an exchange, creating a largerthan necessary opening in the arterial wall undesirably increases thetime required for clotting and long-term recuperation after the surgicalprocedure. This, in part, may result in a costly overnight stay in ahospital. It is highly desirable to reduce these times when possibleeither by not performing conventional introducer sheath exchanges, or byusing the smallest size introducer sheath whenever possible. Reducingthese times may allow such procedures to be performed regularly on anoutpatient basis thereby significantly reducing the overall cost of thesurgical procedure.

II. Providing an Expanded Inner Diameter Introducer Sheath

A. A First Expandable Introducer Sheath of the Present Invention

As seen in FIG. 2A, a first expandable introducer sheath 50 of thepresent invention is shown coaxially disposed within a vessel 56 below asurface of skin tissue 52. The sheath 50 includes an elongate flexibletubular shaft 57 extending between a distal end 58 and a proximal end60. A hub 62 is preferably attached to the proximal end 60 of the sheathvia a strain relief member 61 (FIG. 2B) by means of injection moldingthe hub 62 about the sheath proximal end 60 and strain relief member 61.The hub 62 includes a hemostasis valve 59. A side port 63 extends fromthe hub 62 for connecting with a flexible tube having a 3 way connector(not shown) for interfacing with blood flow management (perfusion) ordrug infusion devices to be in fluid communication with the first sheath50. The shaft 57 of the first sheath 50 is made of a shape-memorypolymer material such as a polyurethane material having a tightlycontrolled glass transition temperature (e.g., 45° C.) that is slightlyabove normal human body temperature.

To employ the first expandable introducer sheath 50 of the presentinvention, the first introducer sheath 50 is initially inserted into thevessel 56 through skin tissue 52 by the method of percutaneous insertionpreviously described for inserting conventional introducer sheathswithin a vessel (see FIGS. 1A-1D and accompanying discussion). Insertingthe first introducer sheath 50 in this manner results in theconfiguration shown in FIG. 2A in which a distal portion of the shaft 57of the first introducer sheath 50 extends coaxially through the vessel56 while a proximal portion of the shaft 57 of the first introducersheath 50 protrudes proximally outward from the surface of skin tissue52. An intravascular device 64, such as a guide catheter inserted intothe first introducer sheath 50, extends through the first introducersheath 50 and distally beyond the distal end 58 of the first introducersheath 50 to extend through the cardiovascular system to a regionadjacent the coronary arteries. A proximal end of the intravasculardevice 64 protrudes proximally out the proximal end 60 of the firstintroducer sheath 50.

Frequently, it is determined that the intravascular device 64 must beexchanged for another, larger intravascular device. In conventionalintroducer sheath systems, the first introducer sheath would have to beremoved and replaced by the larger introducer sheath with a repetitionof the entire percutaneous insertion procedure (FIGS. 1A-1D discussion).However, in the case of the first introducer sheath 50 of the presentinvention, the first introducer sheath 50 can be manipulated to have alarger inner diameter size sufficient to accommodate the larger secondintravascular device without removing the first introducer sheath 50from its position within the vessel. To do so, however, anyintravascular device 64 (with the exception of an unobtrusive wire suchas coronary guide wire) must be removed from the first introducer sheath50.

As seen in FIG. 2B, a mandrel 66 is provided to facilitate employing theinventive first introducer sheath 50. The mandrel 66 is an elongategenerally flexible rod having a distal portion 68 and a proximal end 70with a shaft 69 extending therebetween. The distal portion 68 has arounded conical shape and has a predetermined outer diameter which issubstantially equal to a predetermined outer diameter of the shaft 69.The distal portion 68 has a metallic surface (or other heat conductivematerial) and a heating element 72 carried therein which is capable ofcreating temperatures substantially in excess of the human bodytemperature (e.g., 20° C. greater than 37° C.).

To manipulate the first introducer sheath 50 to have an expanded innerdiameter, the heating element 72 of the mandrel 66 is first activated,and then the distal portion 68 of the mandrel 66 is inserted into theproximal end 60 of the first introducer sheath 50 (through the hub 62)and pushed distally through the sheath 50 as shown in FIG. 2C. With theheating element 72 activated, the mandrel distal portion 68 heats thewall of the first introducer sheath 50 causing the shape-memory polymermaterial of sheath 50 to soften. This permits the mandrel distal portion68 to forcibly expand the walls to form an inner diameter of the firstintroducer sheath 50 equal to an outer diameter of the mandrel distalportion 68 (and shaft 69).

Heating the first introducer sheath 50 in a region 74 adjacent themandrel heating element 72, as seen in FIG. 2C, causes the shape-memorypolymer material of the first introducer sheath 50 to exceed the glasstransition temperature of the polymer material so that the material iseasily stretched. When the polymer material is cooled below the glasstransition temperature, the material will retain whatever shape thematerial is in at the time the material is cooled. Thus, for example, asseen in FIG. 2C, when the mandrel shaft 69 extends through the proximalportion of the first introducer sheath 50, the proximal portions of thesheath which have already cooled will retain an expanded inner diametersize equal to the outer diameter of mandrel shaft 69.

Segments of the sheath polymer material proximal to the heated mandreldistal portion 68 are cooled below the glass transition temperature (45°C.) by the surrounding body tissue and blood flowing about the firstintroducer sheath 50. The blood flowing around the first introducersheath 50 creates a effective heat transfer mechanism and acts toquickly dissipate any heat stored in the first introducer sheath 50 as aresult of the heated mandrel 66. Moreover, the first introducer sheath50 typically is relatively thin (e.g. wall thickness of 0.006-0.011inches) and therefore the first introducer sheath 50 is not readilycapable of storing any substantial quantity of heat. This accentuatesthe transfer of heat from the shape memory polymer material to the bloodand surrounding tissue. Thus, the sheath polymer material is cooled backto near human body temperature (e.g. 37° C.) well below the glasstransition temperature (e.g. 45° C.) almost as soon as the heated distalportion 68 of mandrel 66 moves beyond a region of the sheath that hasbeen heated and forcibly expanded. The expanded inner diameter of thesheath will be retained unless the shape-memory polymer of the firstintroducer sheath 50 is once again reheated above its glass transitiontemperature, and the first introducer sheath 50 reshaped.

The mandrel 66 is pushed distally through the first introducer sheath 50expanding the inner diameter of the first introducer sheath 50 along itsentire length until the distal portion 68 is beyond the distal end 58 ofthe first introducer sheath 50. After pushing the mandrel 66 through theentire length of the first introducer sheath 50, the heating element 72is deactivated and allowed to cool below the glass transitiontemperature of the shape-memory polymer material. The mandrel 66 is thengrasped at its proximal end 70 and withdrawn proximally outward throughthe hub 62 of the first introducer sheath 50 until the mandrel 66 nolonger remains within the first introducer sheath 50. The resultingconfiguration of the expanded inner diameter first introducer sheath 50is illustrated in FIG. 2D.

By comparing the inner diameter of the first introducer sheath 50 inFIG. 2D with the inner diameter of the first introducer sheath 50 inFIG. 2B, one can observe the relative increase (schematically depicted)in the inner diameter of the first introducer sheath 50. The relativeincrease in the inner diameter of the sheath 50 is not actually thisdramatic but has been exaggerated in the drawings for illustrativepurposes. Realistically, the inner diameter of the first introducersheath 50 would be expanded 1 to 3 French sizes, i.e. about 0.013 to0.039 inches. In addition, upon radial expansion of the sheath tubing,little change in wall thickness or length occurs. For example, the wallthickness of the first introducer sheath may be about 0.009 inchesbefore radial expansion and about 0.008 inches after radial expansion.Similarly, a typical length for the first introducer sheath would beabout 4 inches and this length would be about 3.8 inches after radialexpansion.

To expand the inner diameter of the first introducer sheath 50 of theshape-memory material to desired French size (within a suitable range),one merely selects the outer diameter of the mandrel distal portion 68(and shaft 69) to correspond to the desired inner diameter of firstintroducer sheath 50. For example, a size 6 French sheath can be readilyexpanded to a size 7 or 8 French size without substantially shorteningthe length of the sheath or adversely effecting the integrity of thepolymer material.

Once the first introducer sheath 50 has been expanded to the desiredinner diameter, a second intravascular device 80 having a outer diameterlarger than the first intravascular device 64 can be inserted throughthe first introducer sheath 50 in the manner previously described forintravascular device 64. FIG. 2D shows the second intravascular device80 as disposed within the expanded first introducer sheath 50.

The shape-memory material construction of the first introducer sheath 50allows the sheath to be expanded by some number of French sizes while inplace within the vessel 56. This allows the routine use of the smallestsize sheath possible while still accommodating all necessaryintravascular devices. For example, in a case where a smaller sizesheath proved to be inadequate to accommodate all necessaryintravascular devices, the sheath in place would be expanded. Thiscreates, at most, the trauma that would have been required if thatlarger size sheath had been introduced originally but does not createthe substantial additional trauma resulting from the conventionalexchange of a smaller sheath for a larger one. Moreover, much time andeffort is saved because the somewhat tedious multi-step percutaneousinsertion method for an introducer sheath need not be performed again.Instead, a quick and simple insertion of the heated mandrel 66 expandsthe first introducer sheath 50 to the desired inner diameter sizing.Equally important, in a case where the smaller size introducer sheathproved to be sufficient to accommodate all necessary intravasculardevices, the patient has been saved from having a larger than necessaryopening in the vessel wall (e.g., femoral artery wall) as frequentlyhappens when physicians initially choose a larger size introducersheath.

Moreover, although the first expandable introducer sheath 50 has beendescribed as being manipulated (expanded) with no intravascular devicesextending through the sheath 50, a coronary guide wire can remain withinthe sheath 50 while the sheath 50 is being expanded by the heatedmandrel 66.

The first introducer sheath 50 also can be expanded outside thepatient's body (e.g. by means of the heated mandrel) before the sheath50 is inserted into the vessel and before assembly with the dilator 48.This would permit a physician to stock a single size sheath on the shelfand create larger size sheaths only as needed. After being expanded, thesheath 50 would be cooled (while in its expanded size) by the ambientair (e.g. 25° C.) or by a liquid bath having a temperature (e.g. 25° C.or lower) well below the glass transition temperature of the shapememory polymer material of the first sheath 50.

The shape-memory polymer of the first introducer sheath 50 can be madefrom a suitable material having shape-memory characteristics, i.e.,having a glassy state and a rubber state with a tightly controlled glasstransition temperature defining the boundary therebetween. For example,the shape-memory polymer could be made of a ester-based polyurethanematerial having a high elasticity in the rubbery range and a glasstransition temperature of about 45° C. This material is obtainable fromthe Mitsubishi Company and is sold as MM-4510 SMP resin. Alternatively,one can use an alloy polymer material comprising shape-memory materialsuch as an ester-based polyurethane combined with an ordinary(non-shape-memory material) such as an ether-based polyurethane material(such as a material sold under the trade name Pellethane). Theshape-memory polyurethane and ordinary polyurethane material can bemixed in a variety of compositions including a 50/50 composition having50% shape-memory polyurethane and 50% ordinary polyurethane material.The composition can range from 50/50 up to a 90/10 composition of 90%shape-memory polyurethane to 10% of ordinary polyurethane material. Inone combination, an ether-based polyurethane material (the shape-memorypolymer) (#MM4520 from Mitsubishi Company) can be combined with anester-based polyurethane material (Pellethane #2102 or 2355 BR availablefrom the Dow Company of Midland, Mich.). The addition of the ordinarypolyurethane material helps to prevent kinking of the first introducersheath 50 while the sheath material is in the glassy state. The additionof the ordinary polyurethane material softens the sheath tubing morethan using simply 100% polymer shape-memory polymer material and helpsprevent the first introducer sheath 50 from shortening in lengthexcessively upon being radially expanded by the heated mandrel. Ofcourse, other polymeric materials which have shape-memorycharacteristics can be used and other alloying materials known to becombinable with such shape-memory polymers also can be used.

The first introducer sheath 50 can be formed by conventional extrusiontechniques known to one skilled in the art. Although not discussedpreviously, the proximal end 60 of the sheath tubular shaft 57preferably is pre-expanded (by heating) to have an inner diameter atleast as large as the outer diameter of the mandrel shaft 69. Thispre-expanded proximal end 60 of sheath shaft 57 is joined to an innerwall of a distal end of the hub 62 via strain relief member 61 as seenin FIGS. 2A and 2B. Alternatively, the proximal end 60 of sheath shaft57 can be "over expanded" and then shrunk down about an outer wall ofthe distal end of the hub 62 and joined thereto via a strain reliefmember.

The portion of the mandrel 66 proximal to the distal portion 68 is aflexible tubular shaft made of a flouropolymer (e.g., Teflon®),polyethylene, or similar material. A pair of wire leads 71 extendthrough the mandrel shaft 69 to connect the heating element 72 withinthe distal portion 68 to a power source (not shown) outside of themandrel 66. The mandrel heating element 72 can be a wire resistance coilor other suitable means known in the art for producing temperatures inthe surface of distal portion 68 of about 50° C. to 65° C. Thistemperature is sufficient to heat the sheath material over 45° C. yetminimize any possibility of harming the surrounding tissue. A highertemperature producing heating element can be used if a shape memorypolymer having a higher glass transition temperature is employed in thefirst introducer sheath 50. The heating element 72 also should becapable of dissipating heat quickly once the heating element 72 isdeactivated. Moreover, the heating element 72 should produce heat in acontrollable localized area surrounding the heating element 72.

B. A Second Expandable Introducer Sheath of the Present Invention

A second introducer sheath 90 of the present invention is illustrated inFIGS. 3A-3D. The second introducer second introducer sheath 90 has atubular flexible shaft 92 extending from a distal end 94 to a proximalend segment 96. A hub 98 is attached to the proximal end segment 96 ofthe second introducer sheath 90 by a strain relief member 100. The hub98 includes a hemostasis valve 97 for sealing about devices passingthrough the hub 98. The hub 98 also includes a side port 99 forconnecting to an optional side tubing and connector like that shown inFIG. 1A.

The shaft 92 is made of a shape-memory polymer material such aspolyurethane material with a tightly controlled glass transitiontemperature in the body temperature range and the material may includean additive such as an ordinary polyurethane material to comprise analloy as previously described. The shaft 92 is extruded into its tubularshape having an initial inner diameter and an initial outer diameterequal to that shown for the proximal end segment 96 of the secondintroducer sheath 90 located proximally a protective sleeve 102. The hub98 is joined to the proximal end segment 96 when in this initialdiameter size by injection molding the hub 98 about the proximal endsegment 96 and strain relief member 100. Then, by some method of forceapplication (e.g., vacuum, linear stretching, mechanical compression, orthe like) portions of the shaft 92 distally from the proximal endsegment 96 are deformed to assume a smaller inner diameter such as shownin FIG. 3A. The inner diameter of the hub 98 is at least substantiallyequal to the inner diameter of the proximal end segment 96 of the secondintroducer sheath 90, which is the original inner diameter of the sheathshaft 92.

After "forming down" the sheath shaft 92, the protective sleeve 102 isslipped over the sheath shaft 92 to retain the shaft 92 in its reduceddiameter state. The sleeve 102 is formed from a flouropolymer,polyethylene, or similar material. The sleeve 102 is generally inelasticradially at high temperatures above the glass transition temperature ofthe sheath material and is provided to prevent any inadvertent radialre-expansion of the sheath shaft 92 prior to the time such expansion isdesired. The second introducer sheath 90 may be exposed to a variety ofheat sources prior to insertion within the body that would causere-expansion of the shape-memory polymer material comprising the sheathshaft 92 if not somehow constrained as by sleeve 102. For example, heatsources that may include heat during sterilization (e.g. above 100° C.),packaging, or shipping (e.g., up to 80° C.) could cause an unconstrainedsheath shaft 92 to expand to its original inner diameter size because ofthe shape-memory characteristics of the polymer material.

To employ the second introducer sheath 90 of the present invention, thesleeve 102 is first removed from the second introducer sheath 90. Thesecond introducer sheath 90 is then percutaneously inserted into thevessel 56 through skin tissue 52 in the manner described accompanyingFIGS. 1A-1D. This results in the distal end 94 and the shaft 92 of thesecond introducer sheath 90 being disposed coaxially in the vessel 56and the proximal end segment 96 of the second introducer sheath 90 (andhub 98) protruding proximally out of the surface of skin tissue 52, asshown in FIG. 3B. With the second introducer sheath 90 in this position,an intravascular device, such as an angiography catheter or a dilatationcatheter, may be inserted. If it is determined that a largerintravascular catheter is required and that the second introducer sheath90 has an inner diameter too small to accommodate the new intravasculardevice to be inserted, then a larger introducer sheath must be provided.

A mandrel 110 (similar to mandrel 66) as shown in FIG. 3B, is employedto manipulate the second introducer sheath 90 of the present inventionto create a larger inner diameter for accommodating larger intravasculardevices. The mandrel 110 has a distal portion 112 and a proximal end 114with a heating element 116 disposed within the distal portion 112. Thedistal portion 112 is metallic and conducts heat produced by the heatingelement 116. A tubular polyurethane shaft 113 extends from the distalportion 112 to the proximal end 114 and carries a pair of leadsconnecting the heating element 116 to an outside power source (notshown). The shaft 113 may be made of a flouropolymer (e.g., Teflon®),polyethylene, or similar material. The heating element 116 is capable ofbeing activated to reach temperatures of up to about 50° to 65° C.

Once the first smaller size intravascular device has been removed fromthe second introducer sheath 90, the manipulation of the sheath 90 toincrease its size may begin. First, with the heating element 116 of themandrel 110 activated, the distal portion 112 of the mandrel 110 isinserted into the proximal end 96 of the second introducer sheath 90through the hub 98 and pushed distally through the second introducersheath 90 as shown in FIG. 3C. The activated heating element 116 heatsthe walls of the second introducer sheath 90 above the glass transitiontemperature of the shape-memory polymer material causing the walls tosoften. This permits the mandrel distal portion to forcibly expand theinner diameter of the second introducer sheath 90 to a size equal to theouter diameter of the mandrel distal portion 112 and shaft 113. As seenin FIG. 3C, the second introducer sheath 90 is heated in a region 118adjacent the mandrel distal portion 112 and heating element 116 thatcauses the shape-memory material of the second introducer sheath 90 toexceed a glass transition temperature of the shape memory polymermaterial. Because the sheath of shape-memory material had been "shrunkendown" from its original inner diameter size, the shape-memory materialremembers its original shape which tends to help the forcible expansioncaused by the heated mandrel 110.

Thus, with the heating element 116 activated, the mandrel 110 is pusheddistally through the second introducer sheath 90, expanding the innerdiameter of the second introducer sheath 90 along its entire lengthuntil the distal portion 112 is distally beyond the distal end 94 of thesecond introducer sheath 90. As the distal portion 112 (and activatedheating element 116) of the mandrel 110 passes through the tubularsecond introducer sheath 90, portions of the sheath 90 proximal to thedistal portion 112 will naturally cool below glass transitiontemperature of the shape-memory polymer material and "freeze" in aninner diameter equal to that of mandrel shaft 113. As shown in FIG. 3C,portions of the sheath proximal to the mandrel distal portion 112 havebeen expanded to a larger inner diameter. As in the embodiment of firstintroducer sheath 50, a coronary guide wire can remain within the secondintroducer sheath 90 during the expansion of the second introducersheath 90 by the heated mandrel 110.

After pushing the mandrel 110 through the entire length of the secondintroducer sheath 90, the heating element 116 is deactivated and allowedto cool. The mandrel 110 is then grasped at its proximal end 114 andwithdrawn proximally outward through the sheath hub 98 until the mandrel110 is completely removed from the second introducer sheath 90. Theresulting configuration of the second introducer sheath 90 as expandedto its original inner diameter is illustrated in FIG. 3D. As in theillustration of the first introducer sheath 90, the relative increase inthe inner diameter of the second introducer sheath 90 (after "snappingback" to original size) has been exaggerated for illustrative purposes.The relative increase in inner diameter typically would be about 2French sizes.

Once the second introducer sheath 90 has been expanded to the originalinner diameter size, the second intravascular device having an outerdiameter larger than the first intravascular device can be insertedthrough the second introducer sheath 90 in the manner previouslydescribed. A typical length for the second introducer sheath 90 would beabout 4 inches, although the length of the sheath in no way limits theadvantages of the present invention. Similarly, the sheath 90 can havewall thickness of 0.006 inches up to 0.012 inches, and have diameters inthe typical range of 5 to 11 French.

The second introducer sheath 90 preferably is constructed of the samepolyurethane materials (or alloy thereof) as described for the firstintroducer sheath 50. Similarly, the second introducer sheath 90preferably has a similar glass transition temperature (e.g. 45° C.) canbe softened and expanded by means of the mandrel 110 capable of reachingtemperatures of about 50°-65° C. in its distal portion 112. Of course,the mandrel 110 is of similar construction and performs like the mandrel66 used with the first introducer sheath 50.

The first introducer sheath 90 made of the shape-memory polymer materialalso can be formed incorporating a tubular braided wire (or non-metallicmaterial) matrix. This braided matrix would tend to expand radiallyalong with and facilitate the expansion of the shape-memory polymermaterial. This results because the braided material matrix, like theshape-memory polymer, remembers its original size diameter (before beingshrunken down) and when permitted, tends to return to the original sizediameter. The tubular braided matrix also will tend to maintain thesheath 50 in a substantially uniform cylindrical or tubular shape duringthe radial expansion of the sheath 50.

The second introducer sheath 90 provides another way to provide anexpanded inner diameter for an introducer sheath without having toremove the sheath from the vessel. This saves time and reduces trauma tothe vessel wall opening and skin tissue, amongst other advantages of thepresent invention already discussed in the detailed description. Indeed,a unique feature of the second introducer sheath 90 results directlyfrom the use of a shape memory polymer. Because of the characteristicsof the shape-memory polymer material, as the second introducer sheath 90is being expanded, the shape-memory polymer material "remembers" itslarger original size inner diameter and accordingly, tends to facilitatethe forcible expansion of the sheath by the heated mandrel.

C. A Third Expandable Introducer Sheath of the Present Invention

A third expandable introducer sheath 130 of the present invention isillustrated in FIGS. 4A-4G. The third introducer sheath 130 has aflexible tubular shaft 132 extending from a distal end 134 to a proximalend portion 136 of the third introducer sheath 130. A tubular hub 138 isattached to the proximal end portion 136 of the third introducer sheath130 and has a hemostasis valve 139 carried thereon. The hub 138 ispreferably injection molded about the proximal end portion 136 of thesheath 130. The third introducer sheath 130 has a longitudinal fold 140extending along a substantial portion of the length of the shaft 132. Asseen in FIG. 4B, the fold 140 is a portion of a wall 141 of the shaft132 which has been folded over onto itself. The proximal end portion 136of the sheath 130 tapers from the fold 140 to a larger diameter at adistal end of the hub 138. An adhesive 143 or other suitable means suchas ultrasonic welding may be used to temporarily maintain the fold 140against an outer surface of the wall 141 of the sheath 130. The thirdintroducer sheath 130 is shown as coaxially disposed within the vessel56 after insertion through a surface of skin tissue 52 by thepercutaneous technique previously described in conjunction with FIGS.1A-1E.

An angiographic, angioplasty or other diagnostic/therapeutic procedurecan be performed through the third introducer sheath 130 as previouslydescribed for conventional introducer sheaths. If it is determined thatan intravascular catheter is required having an outer diameter largerthan the inner diameter of the folded shaft 132, then the thirdintroducer sheath 130 of the present invention can provide an expandedinner diameter to accommodate the larger intravascular catheter withoutremoval and exchange of the third introducer sheath 130. However, as inthe first and second introducer sheaths (50 and 90), the thirdintroducer sheath 130 provides the opportunity to use a smaller sizeopening in an arterial wall instead of necessarily using a larger sizesheath (and a larger opening) to "play it safe" to avoid performing anexchange. Moreover, the third introducer sheath 130 of the presentinvention (as well as the sheath 50 and 90) also provide the opportunityto have a larger inner diameter sheath without performing a completeintroducer sheath exchange and without removing the sheath 130 fromwithin the vessel.

To expand the inner diameter of third introducer sheath 130, the firstintravascular device (except a coronary guide wire or similarlyunobtrusive intravascular device) must first be removed from the thirdintroducer sheath 130 by proximally withdrawing the device therefrom.Next, a mandrel 142 is provided having a distal portion 144 and aproximal end 146. The distal portion 144 of the mandrel 142 is insertedinto the hub 138 of the third introducer sheath 130 and pushed distallythrough the shaft 132 of the third introducer sheath 130 as seen in FIG.4C. The distal portion 144 of the mandrel 142 has an outer diametergreater than the inner diameter of the sheath shaft 132 in its foldedstate (FIG. 4D). The mandrel 142 also may comprise a mandrel like one ofthose discussed in conjunction with the first or second introducersheaths 50 and 90, respectively. The mandrel 142 may be made of anysuitable generally flexible material, such as a polyethylene material,formed into a tubular configuration. Alternatively, instead of themandrel 142, a guide catheter may be used to cause the fold 140 tounfold.

As the mandrel distal portion 144 is advanced distally through the shaft132, the fold 140 is forced open. This breaks the adhesive seal or bond143 on the wall 141 in a peeling fashion and allows the fold 140 tobegin to unfold as seen in FIG. 4E. This corresponds to the foldingtransition region 145 in FIG. 4C. As seen in FIG. 4C, portions of thethird introducer sheath 130 which are located proximally to the mandreldistal portion 144 are expanded to an extent that they no longer have afold in the wall 141 of the sheath shaft 132. This configuration of thesheath shaft 132 is illustrated in FIG. 4F.

The mandrel distal portion 144 is pushed distally through the shaft 132until it is passed through the entire length of the third introducersheath 130 and exits the distal end 134 of the sheath. This causes thefold 140 to be forced open (i.e., unfolded) along the entire length ofsheath shaft 132 so that the sheath shaft 132 assumes the cross sectionconfiguration shown in FIG. 4F. This is the expanded inner diameter sizeof third introducer sheath 130.

Next, the mandrel 142 is then withdrawn proximally through the thirdintroducer sheath 130 and the hub 138 until the mandrel 142 no longerremains within the third introducer sheath 130. The third introducersheath 130 in its expanded inner diameter configuration is shown in FIG.4G. As seen in FIG. 4G, a second intravascular catheter 148 having aouter diameter larger than the first intravascular catheter is disposedwithin the third introducer sheath 130. In the case where a guidecatheter was used (instead of the mandrel 142) to expand the thirdintroducer sheath 130, the guide catheter would remain within the thirdintroducer sheath 130 as the second intravascular device 148. Otherwise,the second intravascular device 148 would be introduced in the thirdintroducer sheath 130 as previously described. The second intravasculardevice 148 typically would be about 2-3 French sizes larger than theprevious intravascular catheter.

In addition, the third introducer sheath 130 may be made of any suitabletubing material including a shape-memory polymer. If a shape-memorypolymer were used, then the third introducer sheath 130 could beexpanded again beyond the size shown in FIG. 4G by employing a heatedmandrel in a technique similar to that previously described for thefirst introducer sheath 50 of the present invention. However, apolyethylene material or other lubricous coating material (e.g. TEFLON®coated) is preferable. Alternatively, adhesion between the fold 140 andthe wall 141 can be created by using ultrasonic welding techniquesalready known to those skilled in the art.

The third introducer sheath 130 of the present invention may produce arelative increase in inner diameter of about 2 to 4 French sizes. Thiscorresponds to a change of about 0.026 to 0.052 inches. Of course, thedrawings have been exaggerated for illustrative purposes and do notrepresent the appropriate relative change in inner diameter that occurswhen employing the third introducer sheath 130 into its expanded innerdiameter. The third introducer sheath 130 can be of conventional lengthsof about 4 inches and even up to 12 inches. The third introducer sheathpreferably has inner diameters in the folded position corresponding to 5to 9 French sizes.

The third introducer sheath 130 shares the advantages of the otherinventive introducer sheaths already discussed but the sheath can beemployed (unfolded) with a mandrel (or expander) that does not have aheating element or with a guide catheter.

D. A Fourth Expandable Introducer Sheath of the Present Invention

As seen in FIGS. 5A-5D, a fourth expandable introducer sheath 151 of thepresent invention includes an assembly including a first inner sheath150 and a second outer sheath 160. The inner sheath 150 has a shaft 152extending between a distal end 154 and a proximal end 156. A hub 158 isattached to the proximal end 156 of the sheath 150 and has a hemostasisvalve 159 carried therein. The outer sheath 160 has a shaft 162extending between a distal end 164 and a proximal end 166. A hub 168 isattached at the proximal end 166 of sheath 160 and has a hemostasisvalve 169 carried thereon. The outer sheath 160 is coaxially disposedabout the sheath 150 as shown in FIGS. 5A and 5B. The outer diameter ofthe inner sheath shaft 152 is substantially equal to the inner diameterof the outer sheath shaft 162 and the inner sheath 150 is longer thanthe outer sheath 160. The inner sheath 150 may comprise a conventionalintroducer sheath having a length of about 10-12 inches and a 5, 6, orlarger French size inner diameter. The outer sheath 160 also maycomprise a conventional-type introducer sheath, except that it has alength of about 4 inches and an inner diameter that is one to two Frenchsizes larger than the first sheath 150.

To employ the fourth expandable introducer sheath 151, the inner sheath150 is percutaneously inserted in the manner previously described (inconjunction with FIGS. 1A-1E). In the resulting configuration, as seenin FIG. 5A, the inner sheath 150 has a distal portion of its shaft 152extending through the vessel 56 while the distal end 164 of outer sheath160 remains over a proximal portion of the shaft 152 of the inner sheath150 (which remains outside the patient's body). An initial therapeuticor diagnostic procedure using an intravascular device would be performedwith the sheath combination in the position shown in FIG. 5A. If it isdiscovered that an intravascular device having an outer diameter largerthan the inner diameter of the sheath shaft 152 is required, then alarger inner diameter introducer sheath must be provided. The innerdiameter of introducer sheath 151 can be effectively expanded byemploying the inner and outer sheath combination without completeremoval and reinsertion of introducer sheaths.

Whether or not the first smaller intravascular device has been removedfrom the sheath 150, the method of providing an expanded inner diameterintroducer sheath can be initiated. First, the proximal end 156 of theinner sheath 150 is held generally stationary while the shaft 162 of theouter sheath 160 is distally advanced relative to and over the innersheath shaft 152. The distal end 164 of the second outer sheath 160 thusenters the skin tissue 52 and vessel 56 guided by the first inner sheath150. The distal end 164 of the outer sheath 160 is advanced distallythrough the vessel 56 until in the position shown in FIG. 5C, where theproximal end 166 of the outer sheath 160 is just proximally adjacent thesurface of the skin tissue 52. After positioning the outer sheath 160 inthis manner, the inner sheath 150 is withdrawn proximally outward fromthe outer sheath 160 while holding the outer sheath 160 generallystationary in its position within the vessel 56. The inner sheath 150 isfully withdrawn proximally from within the outer sheath 160 as shown inFIG. 5D. If the smaller intravascular device had not yet been removedfrom the inventive introducer assembly it must now be withdrawn in orderto permit introduction of a second, larger device. The inner sheath 150is then discarded and a second intravascular device 170 having an outerdiameter larger than the inner diameter of inner sheath 150 is insertedinto the outer sheath 160 to initiate an additionaldiagnostic/therapeutic procedure using the expanded introducer sheath.

The fourth introducer sheath 151 of the present invention advantageouslyemploys conventional introducer sheath components to provide an expandedinner diameter sheath while maintaining an introducer sheath within thevessel. Moreover, as in the other embodiments of the present invention,the fourth introducer sheath 151 allows the physician to begin aprocedure with a smaller size introducer sheath and not be wary ofhaving to perform a "full-blown" introducer sheath exchange (theprocedure described in discussion accompanying FIGS. 1A-1D).

The outer sheath 160 also can be expanded if necessary to accommodateeven larger size intravascular devices. To do so, the second sheath 160can be made of a shape-memory polymer material. This permits the outersheath 160 to be manipulated in the manner described in association withFIGS. 2A-2E, using a heated mandrel to expand the inner diameter of thesheath 160. Alternatively, the outer sheath 160 could be formed in themanner described in association with FIGS. 3A-3E and manipulated with aheated mandrel to expand the inner diameter of the outer sheath 160.Indeed, even the embodiment of FIGS. 4A-4E could be employed in outersheath 160 so that the inner diameter of outer sheath 160 could beexpanded by pushing a mandrel through the outer sheath 160 to cause afold in the wall of the outer sheath 160 to unfold yielding an expandedinner diameter outer sheath 160.

The use of the fourth expandable introducer sheath 151 (including theinner sheath 150 and the outer sheath 160) includes the insertion of theouter sheath 160 as a separate step from the insertion of the innersheath 150. However, any additional trauma caused by this separate stepin still much less than the trauma created by complete removal of afirst sheath and then insertion of a second sheath requiring duplicationof all the steps for percutaneous insertion. Moreover, the method usingthe fourth introducer sheath 151 saves much time and effort by avoidinga multi-step separate or repeated percutaneous insertion procedure forthe second larger inner diameter sheath.

The inner sheath 150 and outer sheath 160 comprise conventionalintroducer sheaths made of conventional sheath materials such aspolyethylene, ordinary polyurethane, polypropylene, and/orfluoropolymers. The inner sheath 150 typically has a length of about10-12 inches so that the sheath 150 can extend within the vessel 56while still having a sufficient length remaining outside the patient'sbody to carry the outer sheath 160 thereon until ready for use. Thesecond outer sheath 160 is preferably one or two French sizes largerthan the inner sheath 150. For example, the inner sheath 150 can have asize 6 French diameter suitable for angiographic catheters and thesecond outer sheath 160 can have a size 8 French diameter more suitablefor accommodating angioplasty catheters. The first and second sheathsalso have conventional wall thicknesses ranging from 0.006 inches to0.011 inches.

E. A Fifth Expandable Introducer Sheath of the Present Invention

A fifth expandable introducer sheath 181 of the present invention, asillustrated in FIGS. 6A-6E includes an elongate inner sheath 180 havinga flexible shaft 182 extending between a distal end 184 and a proximalend 186 with a hub 188 joined thereon at the proximal end 186. The hub188 includes a hemostasis valve 189 carried therein. As before, theinner sheath 180 is inserted percutaneously in the manner previouslydescribed in conjunction with FIGS. 1A-1E so that the inner sheath 180is disposed within the vessel 56 with a proximal end 186 of the innersheath 180 protruding proximally out of the skin tissue 52.

If it is desired to insert an intravascular catheter having an outerdiameter larger than that allowed by the inner diameter of the innersheath 180, the fifth expandable introducer sheath 181 of the presentinvention can be manipulated to provide an expanded inner diametersheath without requiring a complete removal of the sheath andpercutaneous insertion of another introducer sheath (in the mannerdescribed with FIGS. 1A-1E). The method of expanding the inner diameterof the fifth introducer sheath 181 includes proximally withdrawing theshaft 182 of the inner sheath 180 outward from the vessel 56 and skintissue 52 until in the position shown in FIG. 6B. In this position, asubstantial distal portion of the shaft 182 of the inner sheath 180remains within the vessel 56.

Next, a cylindrical rod 190 (which may have a bore extendingtherethrough to carry intravascular devices therethrough) is insertedinto the proximal end 186 of the inner sheath 180 to obstruct the lumenof the shaft 182. This prevents backbleeding (i.e., blood flow) from thevessel 56 through the inner sheath 180 once the hemostasis valve 189(and hub 188) is removed (as described later). The rod 190 providesrigidity and columnar support to the sheath shaft 182. After the rod 190is firmly seated within the inner sheath 180, the inner sheath 180 iscut or manipulated so that the hub 188 of the inner sheath 180 isremoved, either by cutting the hub 188 off at the shaft 182 or byproviding an otherwise removable hub assembly. This can be accomplishedby various means including a pre-formed transverse slit about thecircumference of the shaft 182 adjacent the proximal end 186 of innersheath 180 or by simply cutting through the shaft 182 with a bladedesigned to make the cut. These proximal portions of the inner sheathwhich are removed are illustrated in phantom in FIG. 6C.

Next, an outer sheath 192 is provided having a flexible elongate shaft191 extending between a distal end 194 and a proximal end 196. The outersheath 192 has a hub 198 similar to the hub 188 and has a hemostasisvalve 199 carried therein. The outer sheath 192 also has an innerdiameter equal to or larger than the outer diameter of the shaft 182 ofthe inner sheath 180. While holding a proximal end of the rod 190 or theinner sheath 180, the distal end 194 of the outer sheath 192 is advanceddistally and coaxially over a proximal end of the rod 190 and the cutproximal end 186 of the inner sheath 180 until a distal end of the outersheath 192 is just proximally adjacent the skin surface 52 as shown inFIG. 6C. While still holding the rod 190 and inner sheath 180 generallystationary, the outer sheath 192 is advanced distally through the skintissue 52 and into the vessel 56, with the rod 190 and inner sheath 180combination serving to guide the advancement of the outer sheath 192.The outer sheath 192 is advanced distally until its hub 198 is justproximally adjacent the skin surface 52 as shown in FIG. 6D. With theouter sheath 192 in place within the vessel 56, the rod 190 and innersheath 180 are withdrawn proximally outward from the outer sheath 192until only the outer sheath 192 remains within the vessel 56 as shown inFIG. 6E. At this point, an intravascular device may be inserted into theouter sheath 192 (of larger inner diameter) to perform anotherdiagnostic or therapeutic procedure.

The outer sheath 192 also can be expanded if necessary to accommodateeven larger size intravascular devices. To do so, the outer sheath 192can be made of a shape-memory polymer material. This permits the outersheath 192 to be manipulated in the manner described in association withFIGS. 2A-2E, using a heated mandrel to expand the inner diameter of thesheath 192. Alternatively, the sheath 192 could be formed in the mannerdescribed in association with FIGS. 3A-3E and manipulated with a heatedmandrel to expand the inner diameter of the sheath 192. Indeed, even theembodiments of FIGS. 4A-4E could be employed in sheath 192 so that theinner diameter of sheath 192 could be expanded by pushing a mandrelthrough the sheath 192 to cause a fold in the wall of the sheath 192 tounfold yielding an expanded inner diameter second sheath 192.

The use of the fifth expandable introducer sheath 181 of the inventiveembodiment illustrated in FIGS. 6A-6E includes the insertion of theouter sheath as a separate step from the insertion of the inner sheath.However, any additional trauma caused by this separate insertion step isstill much less trauma than that created by complete removal of a firstsheath and then insertion of a second sheath requiring duplication ofall the steps for percutaneous insertion. Moreover, the sheath expansionmethod used provided by the sheath combination of inner sheath 180 andouter sheath 192 saves much time and effort by avoiding the multi-steppercutaneous insertion procedure for a second sheath (in the mannerdescribed with FIGS. 1A-1E). More importantly, the fifth expandableintroducer sheath 181 overcomes the much discussed physician's dilemmaof wanting the smaller size introducer sheath yet choosing a larger thennecessary size introducer sheath to avoid having to perform anintroducer sheath exchange. The present invention allows a smaller sizesheath to be used initially and still provide an expanded introducersheath if necessary without having to perform a conventional introducersheath exchange.

F. A Sixth Expandable Introducer Sheath of the Present Invention

A sixth expandable introducer sheath 200 of the present invention, asillustrated in FIGS. 7A-7C includes an elongate flexible shaft 206extending between a distal end 202 and a proximal end 204 with a hub 208joined thereon at the proximal end 204. The hub 208 includes ahemostasis valve 212 carried therein and a connector outlet 210extending from a side of the hub 208. As least one rib 207 extendslongitudinally on an inner wall of the sheath shaft 206. This sheath 200can be inserted percutaneously in a manner previously described inconjunction with FIGS. 1A-1E so that the sheath 200 is disposed withinthe vessel 56 with a proximal end 204 of the sheath 200 protrudingproximally out of the skin tissue 52.

If it is desired to insert an intravascular catheter having an outerdiameter larger than the inner diameter of the inner sheath 180, thesixth expandable introducer sheath 200 of the present invention allowsfor expansion of the inner diameter without requiring a complete removalof the sheath and percutaneous insertion of another introducer sheath(in the manner described with FIGS. 1A-1E).

The shaft 206 of the expandable introducer sheath 200 is made of anelastomeric tubing material such as a polyurethane, latex, Kraton®,silicone rubber or other elastomeric material that is both flexible andstretchable, i.e., capable of being radially expanded by mechanicallyapplied pressure within the sheath shaft 206, such as by the insertionof a guide catheter. This capability is illustrated in FIG. 7A in whichan intravascular device 214 such as a guide catheter is shown extendingwithin the sheath shaft 206. Portions of the shaft 206 of the sheath 200which are distal to a distal end 215 of the intravascular device 214 areshown having a diameter smaller than portions of the sheath shaft 206proximal of the intravascular device distal end 215. These distalportions of the sheath illustrate an original or resting state diameterof the sheath shaft 206. Portions of the sheath shaft 206 proximal tothe intravascular device distal end 215 illustrate the sheath 200 in itsexpanded diameter state wherein the insertion of and presence of theintravascular device 214 within the sheath has forcibly expanded theelastomeric material of the sheath 200 to a larger inner diameter.

FIG. 7B illustrates a sectional view of the expandable introducer sheath200 in a distal region without an intravascular device extending throughthat region. FIG. 7C illustrates a region of the sheath 200 in which theintravascular device 214 extends through the sheath shaft 206 and hascaused the walls of the sheath shaft 206 to stretch and expand about theouter diameter of the intravascular device 214. The rib 207 abutsagainst an outer wall of the intravascular device 214 thereby providingextra spacing between an inner wall of the sheath shaft 206 and an outerwall of the intravascular device 214. This spacing or opening permitsblood-pressure monitoring, blood removal, blood delivery, or druginfusion through the sheath via the hub 208. Although only one rib isshown in the figures, several ribs (the ribs being spaced apartradially) may extend longitudinally along an inner wall of the sheathshaft 206 to provide additional spacing between an outer wall of theintravascular device and an inner wall of the sheath shaft 206.

If desired, the sheath 200 can be reduced to its original smallerdiameter state by simply removing the larger intravascular device 214which allows the sheath shaft 206 to contract back to its originaldiameter by virtue of the elastomeric material characteristics. Thispermits the use of a smaller size sheath if desired after the use of thesheath in its expanded diameter state. However, the introduction of thelarger intravascular device 214 causing expansion of the sheath 200typically expands the opening through the wall of the vessel 56.Accordingly, when the intravascular device 214 is removed and the sheath200 contracts back to its smaller original diameter, blood may flowthrough the puncture site 56 around the sheath.

To diminish any "backflow" of blood in this manner, an elongate solidrod-type dilator may be placed within the sheath to maintain expansionof the larger diameter size of the sheath to prevent such blood flow.However, the rod-type dilator is preferably "stepped" i.e., tapered, tohave larger diameters at its proximal end and smaller diameters at itsdistal portions. Once fully inserted, the rod dilator maintains thesheath 200 in its larger expanded diameter state and then as the roddilator is gradually removed proximally from the sheath and the smallerdiameter portions of the rod dilator pass by the puncture site of theskin tissue 52, the opening of the vessel wall is permitted to graduallyviscoelastically recover and retighten. This diminishes the amount ofblood flow exiting the vessel around the outer diameter of the sheath200 and because the rod dilator is solid, blood flow through the sheath200 is prevented. Accordingly, the use of a tapered diameter roddilator, or "stepwise" tapered rod dilator, increases the possibility ofallowing a hole in the vessel to recover and effectively seal about theoriginal diameter of the sheath shaft once the rod dilator is fullyremoved from the sheath. For example, the puncture size in the vesselthat must be occluded after removal of the introducer sheath 200 wouldbe 6 French (by using the "step" rod dilator) instead of 9 or 10 French.This smaller puncture size potentially reduces hematoma formationfollowing removal of the sheath 200.

However, the sixth expandable introducer sheath 200 is not limited touse with a "step" rod dilator. Alternatively, a uniform diameter roddilator may be used to maintain the sheath 200 in an expanded state toprevent blood flow around the sheath through the puncture site 56. Theuniform rod dilator preferably would have an outer diameter equal to thelargest intravascular device previously extending through the sheath200. As in the use of the "stepped" rod dilator, a conventionalprocedure to occlude the puncture site would be used following removalof the sheath 200 from the vessel.

The sheath 200 should be lubricously coated (by silicone or hydrophyliclubrication) on its inner surface and outer surface to permit smoothmovement of any intravascular devices relative to the sheath. As anexample, the sheath 200 and its original diameter size (i.e., theportions distal of the intravascular device distal end 215 as shown inFIG. 7A) would be a size 6 French diameter. Portions of the sheath 200proximal of the intravascular device end 215 as shown in FIG. 7A couldbe 7, 8, or 9 size French diameter depending upon the outer diameter ofthe intravascular device 214 inserted within the sheath.

In addition, a longitudnal stiffening member such as an elongate wiremay be embedded in a wall of the sheath 200 or within a rib on the innerwall of the sheath 200. The stiffening member would extend a substantialportion of the length of the sheath 200. The stiffening member wouldprovide additional support to prevent potential elongation of the sheath200 when attempting to push a guide catheter (or other intravasculardevice) through the sheath 200. The potential for elongation of thesheath 200 occurs because of the friction caused between the outersurface of the guide catheter and the inner surface of the sheath 200when the guide catheter is pushed through the sheath 200. The stiffeningmember would be incorporated into a sheath 200 in addition to thelubricous coating when the lubricous coating on the sheath 200 alonedoes not sufficiently reduce the friction between the guide catheter andthe sheath 200.

III. Conclusion

The expandable introducer sheath of the present invention facilitatesconvenient percutaneous insertion and removal of multi-sizedintravascular devices. The sheath can be expanded without having toperform a second percutaneous insertion technique to provide an expandedinner diameter sheath within the vessel and while maintaining a sheathwithin the vessel. This avoids re-traumatizing the vessel wall and skintissue at the insertion site by avoiding the need to re-puncture theskin tissue and vessel wall either in the same location or in a secondlocation. The inventive sheath in all embodiments is of simple tubularconstruction having a continuous wall surface and being free of anylongitudinal slits along its length and hub region. This increases theease of handling the sheath and accentuates management of blood flow.The lack of any slits or long free edges having corners reduces thechance of inadvertently dissecting the vessel wall.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

What is claimed is:
 1. A sheath system for introducing intravasculardevices percutaneously, the sheath system comprising:an elongateflexible tubular member for placement within a vessel to slidablyreceive intravascular devices, the tubular member comprising a polymermaterial and including a wall having a continuous outer surface and afirst inner diameter capable of slidably receiving intravascular devicestherethrough and capable of being selectively expanded to a second,larger inner diameter while within the vessel and being maintained inthe second larger inner diameter in a substantially uniform tubularshape without an additional member extending through the tubular member.2. The sheath system of claim 1 wherein the tubular member furthercomprises:a longitudinal fold formed in the wall of the tubular memberextending along a portion of the length of the member and the fold beinglaid over onto the outer surface of wall of the tubular member, the foldcapable of being unfolded to yield the second larger inner diameter ofthe tubular member.
 3. The sheath system of claim 2 wherein the meansfor forcibly expanding further comprises:an elongate mandrel insertableinto the tubular member and having an outer diameter greater than theinner diameter of the tubular member when the fold is laid over onto thewall of the tubular member.
 4. The sheath system of claim 3 wherein themandrel comprises a guide catheter.
 5. The sheath system of claim 1 andfurther comprising:means for forcibly expanding the tubular member fromits first inner diameter to its second larger inner diameter while aportion of the tubular member is in the vessel.
 6. The sheath system ofclaim 1 wherein the polymer material of the tubular member furthercomprises:a shape memory polymer material having a glass transitiontemperature greater than human body temperature wherein the tubularmember is capable of being forcibly expanded from the first innerdiameter to the second larger inner diameter when the shape memorypolymer material is heated above the glass transition temperature and iscapable of retaining the second larger inner diameter when the shapememory polymer material is cooled below the glass transition temperaturewhile being forcibly expanded.
 7. The sheath system of claim 6 andfurther comprising:an elongate mandrel insertable into the tubularmember and having an outer diameter greater than the first innerdiameter of the tubular member, the mandrel having a heating elementdisposed on a distal portion of the mandrel and being capable of heatingportions of the tubular member adjacent the heating element to exceedthe glass transition temperature of the shape memory polymer material.8. The sheath system of claim 6 wherein the shape memory polymermaterial is a polyurethane material with a tightly controlled glasstransition temperature of about 45° C.
 9. The sheath system of claim 6wherein the tubular member is first formed having an inner diameterlarger than the first inner diameter size and then mechanicallymanipulated to have the first inner diameter size.
 10. The sheath systemof claim 1 wherein the tubular member further comprises: a tubularbraided material matrix embedded in the polymer material.
 11. A sheathsystem for introducing intravascular devices percutaneously, the sheathsystem comprising:an elongate flexible tubular member for placementwithin a vessel to slidably receive intravascular devices, the tubularmember comprising a shape memory polymer and having a first innerdiameter capable of being expanded to a second, larger inner diameterand being maintained in the second larger inner diameter in asubstantially uniform tubular shape; and a mandrel having an outerdiameter approximately equal to the second larger predetermined innerdiameter and having a heated distal portion to heat the tubular memberabove a glass transition temperature of the shape memory polymermaterial to permit the outer diameter of the mandrel to forcibly expandthe sheath to the second larger inner diameter and to cool the sheathbelow the glass transition temperature of the shape memory polymer withthe mandrel within the tubular member so that the tubular member retainsthe second larger inner diameter.
 12. A sheath for introducingintravascular devices percutaneously, the sheath comprising:an elongateflexible tubular member for placement within a vessel to slidablyreceive intravascular devices, the tubular member comprising a shapememory polymer material having a glass transition temperature greaterthan human body temperature, and the tubular member having a first innerdiameter capable of being selectively expanded to a second, larger innerdiameter.
 13. The sheath of claim 12 wherein the shape memory polymermaterial is a polyurethane material having a glass transitiontemperature of about 45° C.
 14. A method of introducing intravasculardevices percutaneously comprising:providing an elongate flexible tubularsheath for slidably receiving intravascular catheters, the sheath beingformed primarily of a polymer material and including a wall having acontinuous outer surface and defining a first inner diameter; insertinga distal end of the sheath into a vascular vessel with a proximal end ofthe sheath protruding proximally outward from the vessel; and applying aradial force to the wall of the sheath to expand the sheath to have asecond inner diameter larger than the first inner diameter of the sheathwherein the second larger inner diameter is maintained without anadditional member extending within the sheath.
 15. The method of claim14 wherein the providing step further comprises:forming the sheath froma shape-memory polymer material.
 16. The method of claim 15 wherein thestep of applying force further comprises:providing a mandrel having anouter diameter approximately equal to the second larger predeterminedinner diameter and having a heated distal portion; inserting the mandrelwithin the sheath to heat the sheath above a glass transitiontemperature of the shape memory polymer material to permit the outerdiameter of the mandrel to forcibly expand the sheath to the secondlarger inner diameter; and cooling the sheath below the glass transitiontemperature of the shape memory polymer with the mandrel within thesheath so that the sheath retains the second larger inner diameter. 17.The method of claim 14 wherein the providing step furthercomprises:forming the sheath from an alloy of an ester-basedpolyurethane material and an ester-based polyurethane material.
 18. Themethod of claim 14 wherein the providing step furthercomprises:extruding the sheath to have the second larger inner diameter;shrinking the sheath to assume the first inner diameter; placing atubular sleeve over the shrunken sheath to maintain the first innerdiameter size; and removing the sleeve from the sheath prior toinsertion of the sheath within the vessel.
 19. The method of claim 18wherein the step of applying radial force further comprises:providing amandrel having an outer diameter approximately equal to the secondlarger inner diameter and having a heated distal portion; inserting themandrel within the sheath to heat the sheath above a glass transitiontemperature of the shape memory polymer material to permit the outerdiameter of the mandrel to forcibly expand the sheath to the secondlarger inner diameter; and cooling the sheath below the glass transitiontemperature of the shape memory polymer with the mandrel within thesheath so that the sheath retains the second larger inner diameter. 20.The method of claim 14 wherein the sheath as initially provided has alongitudinal fold in a wall of the sheath extending along a portion ofthe length of the sheath, and wherein the step of applying radial forcefurther comprises;unfolding the fold in the sheath to expand the sheathso that the sheath has the second larger inner diameter that is greaterthan the first inner diameter of the sheath when folded.
 21. The methodof claim 20 wherein the unfolding step further comprises:inserting amandrel into the sheath to expand the sheath from the folded first innerdiameter to the second larger unfolded inner diameter.
 22. A sheath forintroducing intravascular devices percutaneously, the sheathcomprising:an elongate flexible tubular member for placement within avessel to slidably receive intravascular devices, the tubular memberhaving a first inner diameter and comprising a shape memory polymermaterial having a glass transition temperature greater than human bodytemperature wherein the tubular member is capable of being forciblyexpanded from the first inner diameter to a second larger inner diameterwhen the shape memory polymer material is heated above the glasstransition temperature and is capable of retaining the second largerinner diameter when the shape memory polymer material is cooled belowthe glass transition temperature while being forcibly expanded.
 23. Thesheath of claim 22 wherein the shape memory polymer material is apolyurethane material with a tightly controlled glass transitiontemperature of about 45° C.
 24. The sheath of claim 22 wherein thetubular member is first formed having an inner diameter larger than thefirst inner diameter size and then mechanically manipulated to have thefirst inner diameter size.
 25. The sheath of claim 22 wherein thetubular member further comprises:a tubular braided material matrixembedded in the shape memory polymer material.
 26. A method ofintroducing intravascular devices percutaneously comprising:providing anelongate flexible tubular sheath for slidably receiving intravascularcatheters, the sheath being formed primarily ot a shape-memory polymermaterial and including a wall having a continuous outer surface anddefining a first inner diameter; inserting a distal end of the sheathinto a vascular vessel with a proximal end of the sheath protrudingproximally outward from the vessel; providing a mandrel having an outerdiameter approximately equal to a second larger predetermined innerdiameter of the sheath and having a heated distal portion; inserting themandrel within the sheath to heat the sheath above a glass transitiontemperature of the shape memory polymer material to permit the outerdiameter of the mandrel to forcibly expand the sheath to the secondlarger inner diameter; and cooling the sheath below the glass transitiontemperature of the shape memory polymer with the mandrel within thesheath so that the sheath retains the second larger inner diameter. 27.A sheath system for introducing intravascular devices percutaneously,the sheath comprising:an elongate flexible tubular member for placementwithin a vessel to slidably receive intravascular devices, the tubularmember comprising an elastomeric material with a substantially uniformwall thickness, having a wall with a continuous outer surface, andhaving a first inner diameter with a substantially uniform tubular shapecapable of being selectively expanded to a second, larger inner diameterwhile within the vessel and having at least one rib extendinglongitudinally along an inner surface of the wall of the tubular memberwhen the tubular member has the first inner diameter and when thetubular member has the second larger inner diameter.
 28. The sheathsystem of claim 27 and further comprising:an elongate flexibleintravascular device adapted for insertion within the tubular member andhaving an outer diameter equal to the second larger inner diameter ofthe tubular member so that insertion of the intravascular device withinthe tubular member causes radial expansion of the tubular member to itssecond larger inner diameter and the rib on the inner surface of thewall maintaining spacing between the outer diameter of the intravasculardevice and the second inner diameter of the tubular member.
 29. A sheathsystem for introducing intravascular devices percutaneously, the sheathsystem comprising:an elongate flexible tubular member for placementwithin a vessel to slidably receive intravascular devices, the tubularmember comprising a tubular hub and a tubular shaft extending from thehub, the shaft member comprising a polymeric material and including awall having a continuous outer surface and having a first inner diametercapable of slidably receiving intravascular devices therethrough andcapable of being selectively expanded to a second, larger inner diameterwhile within the vessel and being maintained in the second larger innerdiameter in a substantially uniform tubular shape without an additionalmember extending through the tubular member, wherein the hub has aninner diameter at least as large as the second inner diameter of theshaft.
 30. A sheath for introducing intravascular devicespercutaneously, the sheath comprising:an elongate flexible tubularmember for placement within a vessel to slidably receive intravasculardevices, the tubular member including a proximal hub portion and adistal shaft portion extending from the hub portion, the distal shaftportion comprising a shape memory polymer material having a glasstransition temperature greater than human body temperature, and thetubular member having a first inner diameter capable of beingselectively expanded to a second, larger inner diameter, wherein theproximal hub portion has an inner diameter at least as large as thesecond inner diameter of the distal shaft portion.